Increased cord blood IgE concentrations have been related to atopic risk in children, and a previous study reported increased cord blood IgE concentrations in smoking mothers. These associations suggest a relationship between maternal smoking during pregnancy and atopic risk. To evaluate this question, we prospectively studied parental smoking and cord blood IgE and IgD concentrations in a geographically defined group of women belonging to a health maintenance organization. Cord blood samples were obtained from 847 infants born to these women. Cotinine concentrations were measured in 114 cord blood samples to evaluate the veracity of the maternal smoking histories. Smoking during the prenatal period was reported by 144 mothers (17%) and 204 fathers (25%). Decreased birth weight and length were associated with maternal smoking (p less than 0.001 for both), confirming previous studies. Neither maternal nor paternal smoking was found to be associated with IgE level in univariate or multivariate analyses. Maternal and paternal smoking was associated with IgD (p = 0.03 and p = 0.06, respectively) in univariate analysis. In multiple regression analysis controlling for potentially confounding variables, the association between paternal, but not maternal, smoking and IgD was sustained (p = 0.05 and p greater than 0.20, respectively). Our data do not demonstrate that maternal or paternal smoking increases cord blood IgE.